Compositions and Methods for Treating Elevated Secretory Activity

ABSTRACT

Methods for treating diseases characterized by elevated secretory activity using a protease directed to a non-neuronal SNARE protein are described. The protease is produced by selective mutation of a  botulinum  neurotoxin light chain, and is characterized utilizing a reporting construct that includes all or part of the non-neuronal SNARE protein. Such a protease has utility in the treatment of diseases associated with hypersecretion, where the hypersecretion is mediated by a non-neuronal SNARE protein.

This application is a continuation of U.S. patent application Ser. No. 16/557,450, filed Aug. 30, 2019, which is a divisional application of U.S. Pat. No. 10,441,640, filed Aug. 12, 2015, which claims priority to U.S. Provisional Application No. 62/036,412, filed Aug. 12, 2014, and U.S. Provisional Application No. 62/142,400, filed Apr. 2, 2015. These and all other referenced extrinsic materials are incorporated herein by reference in their entirety. Where a definition or use of a term in a reference that is incorporated by reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein is deemed to be controlling.

FIELD OF THE INVENTION

The field of the invention is botulinum neurotoxins.

BACKGROUND

The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

Hyper-secretion from disease-specific cell types is characteristic of many endocrine, immune, and secretory diseases. For example, mast cell secretion underpins anaphylaxis, allergic, autoimmune, and other inflammatory diseases while mucin secretion from epithelial cells contributes to cystic fibrosis (CF) and chronic obstructive pulmonary disease (COPD). Reducing secretion by targeting the core machinery required for secretion can provide a new and effective treatment modality for such diseases. Secretion from such disease-specific cell types is mediated by SNARE proteins, a family of membrane associated proteins that form complexes which mediate vesicle fusion with the plasma membrane and subsequent release of vesicle contents.

Non-neuronal SNAREs are essential for endocrine and metabolic pathways that regulate release of hormones, growth factors, and other signaling molecules. Dysfunction in such secretion pathways results in disease. The non-neuronal Snare protein SNAP-23, for example, is essential for secretion in multiple disease pathways, including IL-6 and TNF release in arthritis, mucin hypersecretion in COPD, CF, and idiopathic bronchiectasis, platelet secretion in blood hemostasis, insulin secretion in diabetes, renin release in blood pressure regulation, and matrix-degrading enzyme release in tumor cell invasion. Similarly, the non-neuronal SNARE protein SNAP-29 is thought to be a negative modulator of neurotransmitter release and a key component in intracellular protein trafficking pathways, with mutations to SNAP-29 resulting in the neurocutaneous syndrome termed CEDNIK.

Blocking secretion by modulating the activity of SNARE proteins has been demonstrated by blocking release of neurotransmitters from motor neurons, using botulinum neurotoxins (BoNTs) to degrade neuronal SNARE proteins that mediate neurotransmitter release. Botulinum neurotoxins (BoNTs), a family of zinc endopeptidases produced by the bacteria Clostridium botulinum, are a powerful class of drugs that are FDA-approved for a wide range of therapeutic and cosmetic applications. There are seven widely recognized BoNT serotypes (BoNT/A through G) and a recently reported serotype H. BoNTs cleave one or more soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins found in motor neurons, blocking neurotransmitter release and leading to flaccid paralysis.

Although among the deadliest natural substances known, BoNTs are widely used in various pharmaceutical and cosmetic applications including cervical dystonia, hyperhidrosis, strabismus, blepharospasm, glabellar lines, and chronic migraine. During intoxication, BoNTs selectively bind to and enter motor neurons via the H chain portion of the molecule. Upon entry into the motor neuron the L chain portion of the molecule is released and degrades the targeted SNARE protein required for controlled neurotransmitter secretion in a highly sequence-specific manner. This results in specific and long-term reduction in the contraction of muscles associated with treated motor neuron. Both binding to motor neurons and degradation of SNAREs utilized in neurotransmitter release are highly specific. For example, BoNT/A, the basis of most BoNT-based pharmaceuticals, blocks secretion from exposed motor neurons by specifically cleaving the protein SNAP-25 but does not bind to other cell types or cleave other SNAP-25 isoforms (such as those expressed in non-neuronal cells). BoNTs have previously been retargeted to non-neuronal cell types through H chain modification. However, therapeutic utility of re-targeted BoNTs is limited by proteolytic specificity for neuronal SNARE proteins. Thus, the therapeutic use of BoNTs are currently limited to neuron-related diseases/conditions and is ineffective for treating non-neuronal secretion disorders.

Thus, there remains a need for BoNTs and/or modified BONTs that exhibit therapeutic secretory inhibition effects in non-neuronal cells.

SUMMARY OF THE INVENTION

The inventive subject matter provides compositions and methods for treating diseases and conditions resulting from elevated secretory activity, utilizing a genetically engineered botulinum neurotoxin.

Embodiments of the inventive concept include methods for treating an individual having a disease characterized by an elevated secretory activity by providing a pharmaceutical that includes a synthetic peptide with a protease activity having substrate specificity for a non-neuronal SNARE protein (such SNAP-23 or SNAP-29). Such a non-neuronal SNARE protein includes an exosite, and the protease includes a mutation of the wild-type botulinum toxin light chain, wherein the mutation comprises a non-native exosite recognition sequence that interacts with the exosite that provides improved binding between the protease and the non-neuronal SNARE protein (relative to a neuronal SNARE protein that acts as a substrate for the wild-type botulinum toxin light chain). The pharmaceutical is administered to the individual on a schedule that reduces secretory activity.

The synthetic peptide can include a targeting moiety, which can bind to cells or tissues associated with the secretory activity. Such a targeting moiety can support binding of the synthetic peptide to a cell and transportation into the cell interior. Suitable targeting moieties include an antibody, and antibody fragment, a receptor ligand, a pharmaceutical compound, a microparticle, and an aptamer.

The wild-type botulinum toxin light chain can be botulinum neurotoxin serotype A (BoNT/A) light chain, botulinum neurotoxin serotype B (BoNT/B) light chain, botulinum neurotoxin serotype C (BoNT/C) light chain, botulinum neurotoxin serotype D (BoNT/D) light chain, botulinum neurotoxin serotype E (BoNT/E) light chain, botulinum neurotoxin serotype F (BoNT/F) light chain, and/or botulinum neurotoxin serotype G (BoNT/G) light chain. Mutations of such a wild-type botulinum neurotoxin light chain to provide the non-native exosite recognition sequence can include one or more mutations to sites corresponding to one or more of the group consisting of Asn136, Ser143, Glu148, Val304, Thr176, His227, Lys337, Leu256, Val258, and Lys356 of SEQ ID NO. 4. The mutation of Asn 136 can be to Ala, Arg, Asp, Cys, Glu, Gln, Gly, His, Ile, Leu, Lys, Met, Phe, Pro, Ser, Thr, Trp, Tyr, or Val. The mutation of Ser143 can be to Asp or Glu. The mutation of Glu148 can be to Met or Val. The mutation of Val304 can be to Asp or Glu. The mutation of Thr176 is selected from the group consisting of Ala, Arg, Asn, Asp, Cys, Glu, Gln, Gly, His, Ile, Leu, Lys, Met, Phe, Pro, Ser, Trp, Tyr, and Val. The mutation of His 227 can be to Ala, Arg, Asn, Asp, Cys, Glu, Gln, Gly, Ile, Leu, Lys, Met, Phe, Pro, Ser, Thr, Trp, Tyr, or Val. The mutation of Lys337 can be to Ala, Arg, Asn, Asp, Cys, Glu, Gln, Gly, His, Ile, Leu, Met, Phe, Pro, Ser, Thr, Trp, Tyr, or Val. The mutation of Leu256 can be to Asp, Ala, or Gly. The mutation of Val258 can be to Asp, Ala, and Gly. The mutation of Lys356 can be to Ala, Arg, Asn, Asp, Cys, Glu, Gln, Gly, His, Ile, Leu, Met, Phe, Pro, Ser, Thr, Trp, Tyr, or Val.

Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B depict exemplary results of a method of the inventive concept. FIG. 1A depicts results of electrophoresis of Strep-Tactin purification of an exemplary botulinum LC, along with results from a set of molecular weight standards. FIG. 1B shows typical results obtained of FRET assays applied to serial dilutions of LC preparations obtained from either 5 mL or 200 μL culture volumes of transfected cells, using a FRET construct with an LC-cleavable region joining a donor fluorophore to an acceptor fluorophore.

FIG. 2 schematically depicts assay methodologies of the inventive concept. Three different entry points for botulinum light chain (LC) into the workflow are shown, representing three different assay methodologies.

FIG. 3 illustrates alignment of two non-neuronal SNAREs (SNAP-23 and SNAP-29) with a portion of the neuronal SNARE SNAP-25 sequence as represented in an exemplary reporting construct directed towards botulinum neurotoxin A or E. The α-exosite and β-exosite recognition regions of the SNAP-25 sequence are indicated, with residues that interact with specified amino acids of the light chain (LC) of botulinum neurotoxin A indicated by arrows. The SNAP-25 cleavage site associated with botulinum neurotoxin A LC activity is also shown.

FIG. 4 shows an exemplary microwell plate where the arrangement of tests performed in individual wells facilitates high throughput testing using methods of the inventive concept.

DETAILED DESCRIPTION

The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

The inventive subject matter provides compositions and methods for producing and identifying compositions that provide a mutated BoNT light chain (LC) that has proteolytic activity with non-neuronal SNARE proteins. Non-neuronal SNARE proteins encompass SNARE proteins involved in secretory processes of non-neuronal cells, including neuroendocrine cells. Selected amino acids within the light chains (LCs) of extant BoNT proteins, such as BoNT/A, can be mutated at one or more sites to provide recognition, substrate specificity, and/or enhanced reaction kinetics for one or more non-neuronal SNARE protein(s), such as SNAP-23 and/or SNAP-29. LC isolation and characterization methodologies that identification of useful or suitable mutated LCs are provided, as are treatment methodologies utilizing such constructs.

One should appreciate that the disclosed compositions and methods provide many advantageous technical effects including provision of specific and long-lasting control of hyper-secretion from non-neuronal cells and relief from associated disease.

As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.

Unless the context dictates the contrary, all ranges set forth herein should be interpreted as being inclusive of their endpoints, and open-ended ranges should be interpreted to include only commercially practical values. Similarly, all lists of values should be considered as inclusive of intermediate values unless the context indicates the contrary. The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value with a range is incorporated into the specification as if it were individually recited herein.

All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.

In embodiments of the inventive concept, modified BoNTs with specificity for non-neuronal SNAREs are derived from native sequences associated with Clostridium botulinum neurotoxins, including BoNT/A, BoNT/B, BoNT/C, BoNT/D, BoNT/E and BoNT/F. These neurotoxins include light chain (LC) portions, for example the light chain of BoNT/A (SEQ ID NO 4) that specifically bind to and exhibit proteolytic activity against neuronal SNAREs. Embodiments of the inventive concept include peptides derived by site-specific mutation of one or more selected amino acids within an LC sequence, as detailed below.

Such mutations can be provided in the form of bacteria, yeast, and/or other cells carrying expression vectors encoding for a peptide of interest. Such expression vectors can be the result of transient infection, and can be inducible or noninducible. The presence of a mutated BoNT LC with enhanced binding to and/or substrate specificity for a non-neuronal SNARE can be identified using an in vitro assay, which lends itself to automation.

BoTest® reporters are used widely used in high throughput screening (HTS) studies to identify BoNT inhibitors and in BoNT-based drug product potency testing. Commercial BoTest® assays utilize a fusion peptide reporter that includes a Förster energy resonance transfer (FRET) pair of peptide fluorophores separated by a portion of a neuronal SNARE protein substrate. Proteolysis of the neuronal SNARE protein substrate results in a separation of the FRET pair, resulting in a change in the observable fluorescent that permits sensitive and accurate quantitative measurement of BoNT proteolytic cleavage. In order to characterize mutated BoNT peptides with the desired non-neuronal SNARE specificity, modified BoTest reporters are provided that incorporate non-neuronal SNARE sequences representative of the desired SNARE protein specificity interposed between the FRET pair of peptide fluorophores. For example, to characterize mutated BoNTs with enhanced binding to and/or substrate specificity for SNAP-23, a reporter construct incorporating all or a portion of the SNAP-23 amino acid sequence (for example, SEQ ID NO 2) interposed between a FRET pair of fluorescent peptides (for example, yellow fluorescent protein and cyan fluorescent protein) can be utilized. Similarly, to facilitate identification of mutated BoNTs with enhanced binding to and/or substrate specificity for SNAP-29, a reporter construct incorporating all or a portion of the SNAP-29 amino acid sequence (for example, SEQ ID NO 3) interposed between a FRET pair of fluorescent peptides (for example, yellow fluorescent protein and cyan fluorescent protein) can be utilized.

In some embodiments, a reporting construct can include an anchoring region. Such an anchoring region can serve to localize the reporting construct to a test surface or membrane. In such embodiments the cleavage site is interposed between the anchoring region and a reporting region (for example, one or more fluorescent proteins). Cleavage of the cleavage site results in release of the reporter from the test surface or from the membrane. This cleavage activity can be detected in any number of ways, including characterization of residual signal from the reporter at the test surface or membrane region, detection of signal from the reporter following release, or loss of signal from the reporter due to degradation of the reporter region following release from the test surface or membrane. In a preferred embodiment, the anchoring region provides localization to a lipid membrane. Suitable lipid membranes include a cell membrane, plasma membrane, vesicle membrane, and/or a lipid layer applied to or supported by a surface. In some embodiments of the inventive concept, the reporting construct can be both expressed and mutated BoNT activity characterized within the same living cell.

As noted above, BoNTs occur in a number of different serotypes: BoNT/A, BoNT/B, BoNT/C, BoNT/D, BoNT/E, BoNT/F, and BoNT/G. A BoNT/H has also been recently proposed. These differ in amino acid sequence, duration of action, and/or substrate specificity. For example both BoNT/A and BoNT/E have substrate specificity for SNAP-25 (SEQ ID NO 1), however BoNT/A has a duration of action of some months whereas BoNT/E has a duration of action of a few days. BoNTs utilized for mutation to alter substrate specificity can be selected, at least in part, on the basis of a desired duration of action. In some embodiments, only the light chain (LC) sequence (i.e. the portion of the BoNT that provides substrate recognition and proteolytic activity) of the selected BoNT is mutated. In a preferred embodiment the LC peptide of BoNT/A (LC/A, SEQ ID NO 4) serves as the basis of the mutated BoNT peptide.

One embodiment of the inventive concept is a method for identifying mutated BoNT peptides that have improved substrate specificity and/or reaction kinetics for a non-neuronal SNARE when compared to a corresponding peptide (i.e. without the mutation(s)) having a native BoNT sequence. Such a mutated BoNT peptide can, for example, demonstrate a binding energy for a non-neuronal SNARE that is 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or greater than that of a corresponding peptide having a native BoNT sequence. Similarly, such a mutated BoNT peptide can show reaction kinetics indicative of proteolytic cleavage of a target non-neuronal SNARE that is 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or greater than that of a corresponding peptide having a native BoNT sequence. In some embodiments, screening studies utilizing modified BoTest reporting constructs, as described above, can be performed on full length or truncated LC sequences to identify those with a desirable characteristic. Use of full-length sequences advantageously provides a more accurate representation of the intact BoNT and supports purification protocols that provide highly purified and active peptide products. In a preferred embodiment, screening studies are performed on full length (448 amino acids) LC/A (SEQ ID NO 4) or LC/A derived sequences. Miniaturized, simplified, and re-optimized protocols for culture volumes ranging from 5 ml to 200 μl cultures can be realized through the use of Strep-Tactin® spin columns.

In an example of a typical screening study, 5 ml and 200 μl cultures produced assayable quantities of LC/A. Using LC/A with the native sequence, complete BoTest® A/E reporter cleavage is typically observed in less than 1 hour with high dilutions (for example, 1:20,000) of a preparation from a 200 μl sample. Extended incubation can improve sensitivity. For example, extending the incubation time to 18 hours typically demonstrates detectable activity from a 1:200,000 dilution of a typical 200 μl-scale preparation of native sequence LC/A. In some embodiments of the inventive concept, a control reporting construct is provided in which the donor and acceptor fluorophores are separated by a cleavage site that is not represented on either neuronal or non-neuronal SNAREs. Such a control reporting construct is useful for determination of nonspecific protease activity, for example due to contamination or undesirable activity on the part of the mutated LC. An example of such a control reporting construct is BoTest® KO, a BoNT-insensitive control version of the BoTest® A/E reporting construct with sensitivity to non-BoNT proteases.

Examples of identification of BoNT LC/A mutations that can recognize the non-neuronal SNARE proteins SNAP-23 and SNAP-29 follow.

LC/A can be obtained from as little as 200 μl of bacterial culture, allowing protein expression in a single well of a 96-well microwell plate (see FIG. 1). As shown, reduction of the culture volume from the conventional 5 mL volume to 200 μl (which can be conveniently accommodated within a single well of a conventional 96 well microwell plate) has no apparent impact on the yield or activity of an LC derived from a transformed cell. Commercially available Strep-Tactin®-coated 96-well plates (from IBA) can be used to perform some or all assay steps in a single well (FIG. 2), as the expressed mutated LC/A binds to the well surface following bacterial lysis and can be purified by washing before assaying. The assay can subsequently be performed by adding a reaction buffer containing a SNAP-23 or SNAP-29 containing reporting construct to the wells and incubating. This method provides high assay throughput and reduced time, cost, and sample manipulation.

As shown in FIG. 2, there are several useful testing strategies. Workflow is similar in all of these testing strategies—culture and induction, followed by lysis of the induced cells and isolation of the expressed LC, followed by characterization of the activity of the expressed LC. The methods differ in the point of entry of the LC into the testing process. In some embodiments, growth and induction, lysis and isolation, and activity testing can occur in the same test well. In other embodiments growth, induction, and lysis is performed in another vessel or test fixture, while isolation of the LC and characterization of its activity take place in the same well of a test plate. In still another embodiment, growth, induction, lysis, and isolation of the LC take place in a vessel(s) and/or a fixture(s) that is separate from the test plate, and the isolated LC is transferred to a well of the test plate for characterization of its activity. In some embodiments, a single test plate may be used to carry out two or more of these testing workflows simultaneously. As shown in FIG. 2, in some instances Strep-Tactin®-coated plates can be used for the entire assay workflow, in others such plates are used only for protein purification and/or screening tests.

As shown in FIG. 2, mutated LC/A-expressing bacteria can be cultured in a conventional 96-well microwell plate and then inoculated into fresh medium in either standard (Strategies 2 and 3 of FIG. 2) or Strep-Tactin®-coated (Strategy 1 of FIG. 2) 96-well plates where they are cultured, induced, and incubated for a period of time sufficient for growth and expression of the mutated LC/A (for example, overnight). Following induction, the bacteria are lysed. Expressed mutated LC/A from the Strep-Tactin®-coated plate cultures binds to the walls of the plate well, while lysed cultures grown in standard plates can be added to Strep-Tactin®-coated plates and tested. Test wells can be subsequently washed with suitable wash buffer (for example phosphate-buffered saline containing 0.1% Tween-20 (PBS-T)) to remove unbound materials. Lysed cultures can also be purified using Strep-Tactin® spin columns and tested in the wells of conventional microwell plates. In some embodiments of the inventive concept a control reporting construct, such as BoTest® KO, is added to at least some test wells to monitor non-specific protease activity.

Since mutants with altered substrate specificity might have altered reaction rates and/or catalytic turnover relative to native LC/A cleavage of SNAP-25 (SEQ ID NO 1), assay detection limits can be determined by titrating the amount of induced bacterial culture used during purification and assaying to determine the dilution that gives a response that differs by about 2, 3, 4, 5, 6, 7, 8, 9, 10 or more standard deviations from that of a control containing no induced culture. In a preferred embodiment, mutated LCs tested in such a fashion produce detectable cleavage of an appropriate detecting peptide construct at a dilution of at least about 1:100 within at least about 4 hours.

SNAP-23 and SNAP-29 reporting peptide constructs can be generated by substituting all or portions of the SNAP-23 and/or SNAP-29 sequence for a corresponding portion of a previously characterized BoNT reporting construct. For example, a SNAP-23 or SNAP-29 reporting peptide construct can be produced by exchanging the SNAP-25 fragment in BoTest® A/E with portions of or full length SNAP-23 (for example, SEQ ID NO 2) and SNAP-29 (for example, SEQ ID NO 3), respectively. Since nominal SNAP-23 and SNAP-29 insertion fragments (SEQ ID NOs 2 and 3, respectively) are slightly shorter than SNAP-25 (SEQ ID NO 1) (FIG. 3); spacer peptide sequences can be added to maintain size consistency across all reporters. Expression vectors can be constructed, expressed, and the resulting reporting peptides purified, for example for in vitro testing purposes. The size, purity, and yield of the reporting constructs thus produced can be quantified. SNAP-23 and SNAP-29 reporting constructs can be tested with BoNT/A and/or BoNT/E to verify lack of substrate activity with these proteases. Cleavage of such constructs by non-BoNT proteases (for example, trypsin) can be used to verify fluorescent peptide performance.

The sites of binding and/or recognition interactions between the BoNT/A light chain (LC) and a portion of SNAP-25 (SEQ ID NO 1) are shown in FIG. 3, along with sequence alignment between SNAP-25 (SEQ ID NO 1) and the non-neuronal SNAREs SNAP-23 (SEQ ID NO 2) and SNAP-29 (SEQ ID NO 3). Specific amino acids involved in the interaction and the corresponding interacting amino acids of the BoNT/A LC are indicated by arrows. The site on SNAP-25 (SEQ ID NO 1) that is cleaved by the BoNT A LC is also shown. The α- and β-exosites indicated represent regions of SNAP-25 (SEQ ID NO 1) that, when occupied, inhibit the reaction with the BoNT/A LC.

Development of modified LC/As with the desired, altered substrate specificity can be accomplished using site-directed LC/A mutagenesis that target critical residues identified as relevant to LC/A::SNAP-25 interaction, thereby generating libraries of mutated LC peptides. Such libraries can be screened for novel substrate specificity and/or reaction kinetics as described above.

Unlike many proteases, BoNTs require large substrates for optimal cleavage. The geometries and compositions of LC active sites are highly conserved across BoNT serotypes, suggesting that substrate specificity arises from LC::substrate binding that first occurs via exosite interactions that orient the substrate, stabilize the complex, and promote additional contacts that poise the LC for cleaving activity. The inventors have realized that cleavage of non-native SNARE isoforms is a function of effective substrate binding, as LC active sites are highly conserved, are not involved in substrate side chain interactions, and the reaction involved in cleavage of the peptide chain does not require the presence of specific amino acid side chains at the cleavage site.

For example, the LC/A contact residues responsible for SNAP-25 (SEQ ID NO 1) interaction are highly or partially conserved in the corresponding residues of SNAP-23 and SNAP-29 (see FIG. 3). A mix of saturation and specific mutagenesis can be used to generate different categories of mutants based on the SNAP domain that they align with, such as the α-exosite, extended linker, and active site residues. BoNT/A LC hydrophobic side-chain interactions that extend along the SNAP-25 α-exosite are largely conserved in SNAP-23 and SNAP-29 (see FIG. 3). However, both SNAP-23 and SNAP-29 contain substitutions at SNAP-25 Asp166, disrupting a salt bridge with LC/A Lys337 and possibly changing binding stability. SNAP-29 also contains a SNAP-25 Gln152 substitution, which potentially affects a polar side chain contact with LC/A Lys356, and an additional non-conservative Gly substitution at SNAP-25 Ile156. Saturation mutagenesis at LC/A Lys356 and Lys337 can be used to generate LC/A mutants that compensate for the loss of the stabilizing salt bridge and polar side-chain contacts on interaction with SNAP-23 and SNAP-29.

A salt bridge between Arg176 of SNAP-25 and Glu148 of LC/A provides a potentially critical anchor point for substrate positioning and that is lost with both SNAP-23 and SNAP-29. Mutant LC/A peptide libraries that reestablish that salt bridge in SNAP-29 can be provided by mutating LC/A Glu148 to Lys or Arg. SNAP-23 contains a Pro substitution at this position, so alternate salt bridges for mutant LC/A directed to this substrate can be provided by mutating Val304 and Ser143 of LC/A to Asp or Glu to exploit the neighboring Lys and Arg residues. A polar side-chain interaction occurs between SNAP-25 (SEQ ID NO 1) Glu183 and LC/A Asn136 and is disrupted in both SNAP-23 and SNAP-29. In SNAP-23, mutant LC/A libraries that compensate for this can be provided by generating a salt bridge by mutating LC/A Asn136 to either Lys or Arg. Similarly, mutant LC/A libraries can also be generated by saturation mutation at this position to screen for mutants that compensate for the Thr substitution in SNAP-29.

The active pockets of SNAP-23 and SNAP-29 include large, positively charged residues (Lys and Arg, respectively) in place of the SNAP-25 Thr200. These substitutions can be accommodated by enlarging the pocket and/or introducing a negatively charged residue at Leu256 and Val258 in LC/A. Asp, Ala, and Gly substitutions can be made at these positions to enlarge and/or make the active pocket more favorable for SNAP-23 and/or SNAP-29. SNAP-29 also contains two significant Lys and Glu substitutions at SNAP-25 Asp193 and Asn196, respectively, that interact with LC/A Thr176 and His227 and result in inverting or introducing charged side-groups. Saturated libraries at LC/A Thr176 and His227 can be constructed to screen for mutants that can accommodate these changes in SNAP-29.

Examples of mutations of the BoNT/A light chain that can be considered suitable for mutated LCs of the inventive concept are summarized in Table 1, which indicates substitutions at specified sites within the sequence of the botulinum serotype A neurotoxin light chain with an “X”. It should be appreciated a mutated LC of the inventive concept can include a single substitution and can also include two or more of these substitutions.

TABLE 1 Substitution Asn136 Ser143 Glu148 Val304 Thr176 His227 Lys337 Leu256 Val258 Lys356 Ala SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID NO 5 NO 30 NO 49 NO 68 NO 87 NO 90 NO 93 Arg SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID NO 6 NO 26 NO 31 NO 50 NO 69 NO 94 Asn SEQ ID SEQ ID SEQ ID SEQ ID NO 32 NO 51 NO 70 NO 95 Asp SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID NO 7 NO 24 NO 28 NO 33 NO 52 NO 71 NO 88 NO 91 NO 96 Cys SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID NO 8 NO 34 NO 53 NO 72 NO 97 Gln SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID NO 9 NO 35 NO 54 NO 73 NO 98 Glu SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID NO 10 NO 25 NO 29 NO 36 NO 55 NO 74 NO 99 Gly SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID NO 11 NO 37 NO 56 NO 75 NO 89 NO 92 NO 100 His SEQ ID SEQ ID SEQ ID SEQ ID NO 12 NO 38 NO 76 NO 101 Ile SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID NO 13 NO 39 NO 57 NO 77 NO 102 Leu SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID NO 14 NO 40 NO 58 NO 78 NO 103 Lys SEQ ID SEQ ID SEQ ID SEQ ID NO 15 NO 27 NO 41 NO 59 Met SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID NO 16 NO 42 NO 60 NO 79 NO 104 Phe SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID NO 17 NO 43 NO 61 NO 80 NO 105 Pro SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID NO 18 NO 44 NO 62 NO 81 NO 106 Ser SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID NO 19 NO 45 NO 63 NO 82 NO 107 Thr SEQ ID SEQ ID SEQ ID SEQ ID NO 20 NO 64 NO 83 NO 108 Trp SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID NO 21 NO 46 NO 65 NO 84 NO 109 Tyr SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID NO 22 NO 47 NO 66 NO 85 NO 110 Val SEQ ID SEQ ID SEQ ID SEQ ID SEQ ID NO 23 NO 48 NO 67 NO 86 NO 111 In other embodiments of the inventive concept, one or more of Asn136, Ser143, Glu148, Val304, Thr176, His227, Lys337, Leu256, Val258, and/or Lys356 can be substituted with any non-corresponding amino acid within LC/A (SEQ ID NO 4) to provide all or part of a protease with enhanced affinity and/or reaction kinetics for a non-neuronal SNARE protein relative to native LC/A.

LC/A mutations with substrate specificity for SNAP-23 and/or SNAP-29 can be identified by generating the appropriate mutation collections and testing against SNAP-23 and SNAP-29 reporting constructs. In a typical example of a testing protocol, a 96-well microwell plate can accommodate 20 mutant LC/A peptides plus controls, allowing the rapid processing of peptide library contents. Single colonies from the mutant LC library colonies can be cultured and assayed. The original colonies can be stored at 4° C. during testing to permit clone recovery and/or retesting. Generally, plates can be evaluated only if a positive (i.e. wild-type) LC/A control shows full cleavage of BoTest® A/E and no significant (i.e. <10%) negative control reporting construct (for example, BoTest® KO) cleavage after 4 hours of incubation with these reporting peptide constructs. Plates that initially fail these criteria can be retested. A positive mutant LC/A can be defined as any mutant LC/A that shows greater than about 20% appropriate reporter cleavage in one or both samples of a duplicate. The original parental culture for any positive result can be cultured, and glycerol stocks generated and banked. All positive clones can be retested, and clones that retest positive can be banked and fully sequenced to identify mutations. Clones that show positive results can be verified, for example using recombinant full-length SNAP-23 or SNAP-29 and protein blot analysis to confirm substrate cleavage, and can be transfected into cells to measure secretion reduction in vivo.

The integrated growth/induction, lysis, isolation, and activity assays described above make identification of such mutant LCs possible. In some embodiments, however, it can be useful to implement high throughput, automated, or semi-automated (i.e. combining manual and automated steps) screening methods to facilitate such identification. In some embodiments of the inventive concept, such methods can be implemented using a 24, 48, 96, 384, and/or 1,536 well plate. In some embodiments all of the steps of growth, induction, lysis, isolation, and activity testing are performed on a single plate. In other embodiments these steps can be performed across two or more plates for a given mutant LC chain being characterized. In still other embodiments, one or more of these steps can be performed offline (for example, using a small affinity column for isolation of the mutant LC) prior to addition to a well of a microwell plate.

An exemplary arrangement of a 96-well microwell plate that facilitates high throughput and/or automated testing of LC mutations for screening purposes is shown in FIG. 4. As shown, the plate includes LC/A positive and empty vector negative controls that are tested using a BoTest A/E reporting construct and a non-specific protease directed reporting construct (for example, BoTest KO). LC mutations can be tested using reporting constructs carrying suitable non-neuronal SNARE proteins (for example, SNAP-23 or SNAP-29) or cleavage fragments thereof interposed between donor and acceptor fluorophores of a FRET pair. In the plate layout depicted, each LC mutation is tested against such a non-neuronal SNARE reporting construct in duplicate. In addition, every fifth LC mutation is tested against a non-specific protease directed reporting construct (such as BoTest KO) in duplicate as a control.

It should be appreciated that light chain sequences identified as having the desired activity for non-neuronal SNARE proteins can be combined with a targeting moiety that provides selective binding to a non-neuronal cell. Suitable targeting moieties include native or mutated botulinum heavy chain sequences which, when combined with an LC, provide an intact, functional protein capable of targeting cells, being internalized, and being processed. In some embodiments of the inventive concept, one or more mutant LC chains are combined with one or more native or mutated heavy chains of BoNT/A, BoNT/B, BoNT/C, BoNT/D, BoNT/E, BoNT/F and/or BoNT/G. It should be appreciated that a mutant LC derived from a given BoNT serotype can be combined with a native sequence or mutated heavy chain from a corresponding BoNT serotype or a different BoNT serotype. In other embodiments of the inventive concept, one or more mutant LCs are combined with one or more mutated botulinum heavy chains that show altered cellular specificity for a desired cell type.

In other embodiments of the inventive concept, a targeting moiety can be a peptide or other molecule that does not correspond to a botulinum neurotoxin heavy chain. For example, a targeting moiety can be an antibody, and antibody fragment, or a single chain antibody. In other embodiments a targeting moiety can be a ligand for a cell surface receptor (for example, a drug, hormone, saccharide, polysaccharide, or lipopolysaccharide), or a receptor for a ligand existing on the surface of the target cell (for example, a lectin). In other embodiments, the targeting moiety can be one member of an affinity pair (for example, biotin and avidin), with the other member of the affinity pair having (or being part of a molecule that has) an affinity for the target cell. In still other embodiments, a non-peptide macromolecule (such as an aptamer) can be used as a targeting moiety. In some embodiments, a targeting moiety can be joined to a mutant LC by a linker peptide. Such linker peptides can be selected to be flexible (for example, to reduce steric hindrance) or can be selected to be rigid (for example, to provide a desired geometry). In some embodiments the linker peptide is selected to be cleaved or degraded by cellular processes following internalization, thereby releasing the mutant LC.

Another embodiment of the inventive concept is a method for treating an individual with a disease characterized by hypersecretion. In such a method, a drug composition that includes a mutant LC targeting a non-neuronal SNARE is administered to the patient having such a disease or in need of such treatment. In such an embodiment, the mutant LC can be selected to have substrate specificity and/or enhanced reaction kinetics (relative to the native sequence LC from which it is derived) for one or more non-neuronal SNARE proteins associated with secretion, where such a SNARE protein(s) is found in a cell characterized by hypersecretion in the afflicted individual. Such a drug composition can be in the form of an injectable liquid, and in such form can include buffers and preservatives suitable for intravenous, intramuscular, subdermal, intraocular, peritoneal, and/or central nervous system usage. In other embodiments the drug composition can be supplied as a topical preparation, such as a suspension, ointment, gel, lotion, or cream. In such embodiments the drug composition can include additional ingredients, such as emollients, excipients, and/or agents that aid in transdermal delivery. In some of such embodiments, the drug composition can be supplied in the form of a patch or film that is applied topically. In still other embodiments, the drug composition can be supplied in a form that facilitates transmucosal delivery. In such embodiments the drug composition can be supplied as an inhaled substance (for example, a powder, vapor, and/or droplet mist), a sublingual drop or lozenge, a nasal spray, an eye drop, suppository, or pessary. In still other embodiments the drug composition can be supplied for oral consumption, for example as a consumable liquid or food. In such embodiments the drug composition can include colorants, flavorants, and/or thickening agents. When packaged for oral administration, a drug composition including a mutant LC can include formulations or mechanisms to delay release and/or absorption until a desired location with the gastrointestinal tract is reached (for example, time release coatings, capsules with perforations, etc.).

Treatment of a hypersecretion disease using a modified LC light chain can be performed using a dosing/schedule that permits effective treatment while minimizing undesired effects. For example, a mutant LC of the inventive concept can be administered at dosages ranging from 1 μg/kg body weight to 100 mg/kg body weight. In some embodiments of the inventive concept, a single dose of a drug composition including a mutant LC of the inventive concept can be sufficient to derive a beneficial effect. In other embodiments of the inventive concept multiple doses over a period of time are administered. For example, relatively small doses of a drug composition including the mutant LC can be administered on a regular schedule (e.g. every other day, daily, two to 12 times a day) until the desired result is achieved. Due to their method of action a drug composition containing a mutant LC can have an extended effect once the desired therapeutic effect is achieved. As noted above, the duration of this effect can be selected based, at least in part, on the selection of the native LC sequence from which the mutant LC is derived. In some embodiments, therapeutic effects may persist for at least 3 months following administration of the mutant LC. In other embodiments, therapeutic effects may persist for a day, 3 days, a week, 2 weeks, 3 weeks, 4 weeks, 6 weeks, 8 weeks, or more following administration of an effective dose of the mutant LC.

In some embodiments of the inventive concept, a series of mutant LCs having similar substrate specificities but different sequences can be administered to reduce the effect of patient antibodies developed to a mutant LC and/or to reduce the induction of such an antibody response in a patient treated with such compositions. In still other embodiments, a mixture of mutant LCs having similar substrate specificities but different sequences can be administered, thereby reducing the concentration of each mutant LC below a level likely to induce a significant immune response while maintaining a therapeutic effect. Similarly, mutant LC can be modified to reduce antigenicity (for example, via PEGylation).

It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refer to at least one of something selected from the group consisting of A, B, C . . . and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc. 

What is claimed is:
 1. A method of treating an individual having a disease characterized by an elevated secretory activity, comprising: providing a pharmaceutical comprising a synthetic peptide having a protease activity characterized by substrate specificity for a non-neuronal SNARE protein having an exosite, wherein the protease comprises a mutation of a wild-type botulinum toxin light chain, wherein the mutation comprises a non-native exosite recognition sequence that interacts with the exosite of the non-neuronal SNARE protein, and wherein the mutation is selected to provide improved binding between the protease and the non-neuronal SNARE protein relative to a neuronal SNARE protein that acts as a substrate for the wild-type botulinum toxin light chain; and administering the pharmaceutical to the individual on a schedule effective to reduce the secretory activity.
 2. The method of claim 1, wherein the synthetic peptide comprises a targeting moiety.
 3. The method of claim 2, wherein the targeting moiety binds to cells or tissues associated with the secretory activity.
 4. The method of claim 2, wherein the targeting moiety supports binding of the synthetic peptide to a cell and transportation to the cell interior.
 5. The method of claim 2, wherein the targeting moiety is selected from the group consisting of an antibody, and antibody fragment, a receptor ligand, a pharmaceutical compound, a microparticle, and an aptamer.
 6. The method of claim 1, wherein the wild-type botulinum toxin light chain is selected from the group consisting of botulinum neurotoxin serotype A (BoNT/A) light chain, botulinum neurotoxin serotype B (BoNT/B) light chain, botulinum neurotoxin serotype C (BoNT/C) light chain, botulinum neurotoxin serotype D (BoNT/D) light chain, botulinum neurotoxin serotype E (BoNT/E) light chain, botulinum neurotoxin serotype F (BoNT/F) light chain, and botulinum neurotoxin serotype G (BoNT/G) light chain.
 7. The method of claim 1, wherein the non-native exosite recognition sequence comprises one or more mutations to sites corresponding to one or more of the group consisting of Asn136, Ser143, Glu148, Val304, Thr176, His227, Lys337, Leu256, Val258, and Lys356 of SEQ ID NO.
 4. 8. The method of claim 7, wherein the mutation of Asn 136 is selected from the group consisting of Ala, Arg, Asp, Cys, Glu, Gln, Gly, His, Ile, Leu, Lys, Met, Phe, Pro, Ser, Thr, Trp, Tyr, and Val.
 9. The method of claim 7, wherein the mutation of Ser143 is selected from the group consisting of Asp and Glu.
 10. The protease of claim 7, wherein the mutation of Glu148 is selected from the group consisting of Met and Val.
 11. The method of claim 7, wherein the mutation of Val304 is selected from the group consisting of Asp and Glu.
 12. The method of claim 7, wherein the mutation of Thr176 is selected from the group consisting of Ala, Arg, Asn, Asp, Cys, Glu, Gln, Gly, His, Ile, Leu, Lys, Met, Phe, Pro, Ser, Trp, Tyr, and Val.
 13. The method of claim 7, wherein the mutation of His 227 is selected from the group consisting of Ala, Arg, Asn, Asp, Cys, Glu, Gln, Gly, Ile, Leu, Lys, Met, Phe, Pro, Ser, Thr, Trp, Tyr, and Val.
 14. The method of claim 7, wherein the mutation of Lys337 is selected from the group consisting of Ala, Arg, Asn, Asp, Cys, Glu, Gln, Gly, His, Ile, Leu, Met, Phe, Pro, Ser, Thr, Trp, Tyr, and Val.
 15. The method of claim 7, wherein the mutation of Leu256 is selected from the group consisting of Asp, Ala, and Gly.
 16. The method of claim 7, wherein the mutation of Val258 is selected from the group consisting of Asp, Ala, and Gly.
 17. The method of claim 7, wherein the mutation of Lys356 is selected from the group consisting of Ala, Arg, Asn, Asp, Cys, Glu, Gln, Gly, His, Ile, Leu, Met, Phe, Pro, Ser, Thr, Trp, Tyr, and Val.
 18. The method of claim 1, wherein the non-neuronal SNARE protein is selected from the group consisting of SNAP-23 and SNAP-29. 